In multi-range hydromechanical steering transmissions of the synchronous shifting type, such as exemplified in applicant's U.S. Pat. Nos. 4,682,515 and 4,799,401, two hydrostatic drive units are uniformly stroked in one direction to accelerate through one transmission output range, and, upon shifting to the next higher transmission output range, the hydrostatic drive units are uniformly stroked in the opposite directions to accelerate through this higher range. To effectively implement such synchronous range shifting without changing hydrostatic unit stroke, a steer-cancelling or hydrostatic output speed averaging gear train is required. This gear train includes a shaft which normally extends through the central openings in the hydraulic pump and motor set of each hydrostatic unit. Consequently, the main transmission cross-shaft interconnecting the left and right output combining sets must be located elsewhere. This renders synchronous-shifting, hydromechanical steering transmissions somewhat bulky and thus difficult to package within modern track-laying or skid-steered vehicles with their stringent space and weight limitations.